1. Technical Field
An accessory for a printer tray is disclosed. More specifically, a device is disclosed for holding the top sheets of a stack in a flat position in a printer tray when the sheet material is prone to curling as a result of changes in humidity, temperature, age, etc. The disclosed hold-down device prevents such curling at the leading edge and subsequent jamming of the feed mechanism of a printer as a result of the curling. While the disclosed accessory is particularly useful for multiple-ply or integrated forms, which are particularly prone to curling, the disclosed accessory can be used with all types of sheet material, including single ply sheets or stock.
2. Description of the Related Art
A laser printer is a common type of computer printer that rapidly produces high quality text and graphics on plain paper as well as multiple-ply forms or integrated forms. As with digital photocopiers and multifunction printers (MFPs), laser printers employ a xerographic printing process but differ from analog photocopiers in that the image is produced by the direct scanning of a laser beam across the photoreceptor of the printer.
Laser printers have many significant advantages over other types of printers. Unlike impact printers, laser printer speed can vary widely, and depending upon the graphic intensity and other factors. Fast laser printers can print over 200 monochrome pages per minute (12,000 pages per hour). Fast color laser printers can print over 100 pages per minute (6000 pages per hour). High-speed laser printers are used for mass mailings of personalized documents, such as credit card or utility bills, and are competing with lithography in some commercial applications.
Laser printers are also being used to print multiple-ply forms and integrated forms that may include both shipping information and a return mailing label on a single top sheet. Such multiple-ply forms include a backing sheet, a layer of adhesive and a top printed sheet which may include perforations or slits for removing certain parts of a form, such as a return mailing label from the remaining portions of the top sheet, such as the original shipping information.
Inkjet printers come in many different types and sizes they are mostly used as desktop printers and most of them are able to print in color. Inkjet printers are generally cheaper to buy than laser printers, however they are more expensive to maintain. Cartridges need to be changed more frequently and special paper may be needed to produce a good quality image. Most inkjet printers work by spraying small ink onto paper through tiny nozzles. Spraying is initiated by heating the ink to create a bubble until the pressure forces it to burst and hit the paper. Then the nozzle is closed and the process repeated thousands of times per second. Inkjet printers can also be used to print multiple-ply forms and integrated forms that may include shipping information and a return mailing label.
Although the inkjet and laser printers have replaced most dot matrix printers, many companies still own dot matrix printers for forms. Dot matrix printers are impact printers; they create images by striking an inked ribbon onto a paper using pins and make more noise and provide lower resolution than laser and inkjet printers. While not as popular as laser printers, dot matrix printers can be used to print multiple-ply forms an integrated forms.
Most inkjet and laser printers have a paper tray for holding a stack of paper or, in the case of the present disclosure, a stack of multiple-ply or integrated forms. Most printers also include single-sheet feeders or feed trays. The mechanism that draws a sheet or form into the printer and towards the printing path is often referred to as the “feed mechanism.” A typical printer feed mechanism includes multiple pairs of laterally spaced-apart opposing rollers that are used to pull the top sheet or form in from the tray or feeder and advance the sheet towards the printing area.
A common problem associated with all types of printers that rely upon sets of rollers to pull single sheets from a stack of sheets is the phenomenon known as “jamming.” Specifically, one lateral portion of a leading edge of a sheet may fit neatly between a pair of opposing rollers while an opposite lateral portion of the leading edge of the sheet engages the upper or lower roller of another pair of rollers causing part of the sheet to be pulled inside the printer and the other portion of the sheet to be crumpled against the rollers. Further, as pairs of rollers and belts are used to pull a sheet through the tortuous printing path, jamming can occur downstream along the printing path within the printer as well.
The jamming problem is particularly problematic when printing multiple-ply sheets or integrated forms that include a backing or release layer, an adhesive layer and a label layer attached to the backing layer by the adhesive layer. The materials used for the backing layer and the label layer are different. Backing or release layers are typically thin sheets of waxed or silicon-coated paper while the label layers are fabricated from thicker sheets of paper and carry a layer of adhesive. As a result, the backing and label layers absorb water or are affected by humidity differently. The backing and label layers may also react to temperature changes or other environmental changes differently. Further, the backing and label layers may also deteriorate or age differently. As a result, multiple-ply integrated forms or labels are prone to curl in response to various environmental changes. When the integrated forms are placed in a tray of the laser printer or an inkjet printer, such curling can cause jamming at the initial feed mechanism or downstream in the printing path. The jamming of the printer causes frustration to the user and may also require professional maintenance to repair the printer. In addition to multiple-ply or integrated forms, environmental conditions can cause other forms of sheet material to curl, including single-ply sheets and certain types of paper stock.
As a result, there is a need for an improved device for supplying sheet materials to printer feed mechanisms that will reduce the incidence of jamming associated with multiple-ply labels, integrated forms and other sheet materials prone to curling.